This invention relates to an arrangement for the generation of sound fields of a specific modal composition as simulated sound source for acoustic investigations, in particular for the simulation of the sound produced by rotor-stator arrangements of turbomachines, for active sound amplification, or as an opposing sound field for active sound reduction.
In many technical sectors, the application and operation of certain equipment, for example aircraft propulsion units, automobile drive units, compressors, gas turbines, venting systems, fans and the like, involves an undesired, aero-acoustic sound level. With such equipment, for example rotor-stator systems of compressors and gas turbines, the performance of investigations into the causes of generation and propagation of air-borne noise or into measures for noise attenuation using a real-life test arrangement involves considerable technical investment. In the case of turbomachines, such investigations can be performed with rotor-stator arrangements which, due to the necessary drive units, the moving components, the high weight and the required control mechanisms, are complicated and expensive. In addition, the generation of a simulated sound field for test purposes or as opposing sound field for active sound reduction, as described, for example, in U.S. Specifications U.S. Pat. No. 5,702,230 or U.S. Pat. No. 5,590,849, also requires considerable apparatus, control and energetic investment for the provision and operation of active elements, such as loudspeakers or piezo-electric sound sources. Additional problems arise from the provision of powerful actuators, their high weight, power demand and operation at elevated temperatures, pressures and velocities of flow.